Moenuronic acid: synthetic studies and absolute configuration

The absolute configuration of the moenuronic acid moiety of the antibiotic moenomycin A has been established by a partial synthesis starting from D-galactose. The relation between the absolute conformation of α-hydroxy lactones and their chiroptical properties is discussed in detail.     

Über die Resonanzwellenlängen axialer Luftschwingungen in offenen Rohren

The characteristic wave-lengths of axially symmetric air vibrations in open circular tubes are evaluated. The solution takes into account the exact value of the reflection coefficient of the mouth given byLevine andSchwinger. Experimental results verify the theoretical curves.     

Präparation und Lumineszenzeigenschaften von Zinkoxid

ZnO-phosphor powders are produced in systematic preparation series by annealing in an atmosphere containing H₂ or O₂. The samples have different quantum efficiencies, thermoluminescence light sums, and glow curve forms. The following explanation for the luminescence mechanism of ZnO can be confirmed: 1. The green luminescence is caused by intrinsic lattice imperfections. 2. Oxygen defects are the activators for the green luminescence. 3. Oxygen ions on interstitial sites produce hole traps, the energetic depth of which is caused by different coupling with oxygen defects.     

Einfluß der Wechselwirkung im Endzustand auf die Elektrospaltung des Deuterons in der Nähe der Schwelle

Dispersion relations are used to calculate thel=0 matrixelement for the electrodisintegration of the deuteron. To treat the final state interaction the phase shifts for the nucleon-nucleon scattering were taken from experiment. Approximations for the cuts often used in connection with dispersion relations are considered in the frame of potential theory. An effective range approximation is discussed. For the singular integral equations which occur in problems of this kind we give a solution which avoids the difficulties, that otherwise may arise from the deuteron pole.     

Adaptions- und Zerlegungseigenschaften von Maßen

Ohne Zusammenfassung     

On the connection of the Independent-Pair Model with a variational principle

It is shown thatBrenig's method of deriving the basic equations of the Independent-Pair Model can also be understood from a variational principle applied to the pseudoexpectation value 〈п¦H¦Ψ〉 (п=model wave function,Ψ=true wave function). Deviations from a vanishing first and second variation of 〈п¦H¦Ψ〉 with respect to the model wave functionп are shown to be due only to the independent-pair approximation, and thus permit us to make a qualitative estimate of the accuracy of this method.     

Zum Magnetismus von aufgedampften Silber-Mangan-Legierungen

Ag-Mn alloys are produced by simultaneous condensation of both components on a substrate at 30 °K. By this method one gets a statistic distribution of the Mn atoms in Ag. The susceptibility of unannealed films obeys Curie's law for all Mn concentrations up to 16 at. per cent. Above that concentration the Curie-Weiss law holds with a negative paramagnetic Curie temperature. The magnetic moment decreases with increasing Mn concentration. For small concentrations the magnetic moment of a Mn atom corresponds to a spin of 4/2. The temperature of spin ordering is proportional to the Mn concentration. Annealing the films to 300 °K changes the distribution of the Mn atoms and the magnetic properties. The magnetic measurements on annealed films qualitatively agree with known measurements on molten Ag-Mn alloys. The magnetic properties are discussed by using theoretical arguments given byFriedel, Ziman, andOverhauser.